Mechanical behaviors, lattice thermal conductivity and vibrational properties of a new MAX phase Lu2SnC

In this work we examine, via density functional theory (DFT), material properties of the recently synthesized Lu-based MAX phase Lu2SnC and facilitate comparison with the Sn-containing MAX phases M2SnC (where M = Ti, Zr, Hf and Nb). Structural, elastic, mechanical, thermal and vibrational properties of Lu2SnC are calculated for the first time. In regard to the elastic properties and the mechanical behavior, it is predicted that Lu2SnC is softer and more easily machinable than the other examined M2SnC phases. All the M2SnC phases, including Lu2SnC, are mechanically and dynamically stable and elastically anisotropic. Calculated acoustic Debye temperature is lowest for Lu2SnC among the examined M2SnC phases. Clarke's and Slack's approximation models are employed to estimate the minimum and lattice thermal conductivities for all the 211 MAX compounds under study. Lu2SnC should have candidacy for thermal barrier coating (TBC) material because of its high thermal shock resistance, low minimum thermal conductivity, high melting point and characteristically good oxidation resistance. Ab-initio calculations presented in this study should be complementary to future experimental and theoretical work which can lead to further insights.